SpanDSP is a library of DSP functions for telephony, in the 8000 sample
per second world of E1s, T1s, and higher order PCM channels. It contains
low level functions, such as basic filters. It also contains higher
level functions, such as cadenced supervisory tone detection, and a
complete software FAX machine.  The software has been designed to avoid
intellectual property issues, using mature techniques where all relevant
patents have expired. See the file DueDiligence for important
information about these intellectual property issues.
